The invention relates to a semiconductor component with interface functions between the controller and the power components of power converters, suitable for controlling semiconductor components. In particular the present invention related to a semiconductor component for controlling IGBT power switches.
Hybrid control circuits are known from prior art. Such circuit arrangements to control semiconductor power switches are described in the Applikationsbuch IGBT-und MOSFET-Leistungsmodule [Applications for IGBT and MOSFET Power Modules] (ISBN 3-932633-24-5) and in Catalogue '99 of SEMIKRON Electronic GmbH. To explain the control problems, block diagrams will be referred to below.
FIG. 1 shows the principal design of a power electronics system for controlling state-of-art high-voltage IGBTs (Insulated Gate Bipolar Transistors).
In detail, a power electronics system consists of a controller 1 with, for example, microprocessor, memory and A/D or D/A transformer unit. A control circuit 2 has digital, analogue and power components for signal processing, a power supply and error processing. Potential separation 3 is between the low-voltage and high-voltage side. The driver circuit 4 has power supply, gate driver and monitoring. There is an intermediate voltage circuit 5, power switches 6, a load 7, and sensors with evaluation circuits 8.
To demonstrate the connection to the power semiconductor switches, two IGBTs of a half-bridge, the intermediate voltage circuit of the converter and the load (here represented by the motor) are drawn as cutouts from a converter circuit.
The compatible data for recording the state variables of the converter in operation are supplied by sensors for all relevant operating parameters with possible evaluation circuits, with which the state variables of the load and the power switches (e.g. RPM, position, torque or temperature, voltage, current and short circuit) are recorded and transmitted to the control circuit or the controller.
For low-current applications (such as battery or automotive applications with intermediate voltages smaller than 100 V), semiconductor technologies exist today which allow the largely monolithic integration of the controller, the control and driver circuit, potential separation and the recording of state variables. In the case of higher intermediate voltages, the integration of potential separation (or the level converter step) becomes more difficult because of isolation problems. Solutions for the integration of level converter steps up to 600 V and recently also up to 1200 V are found in prior art and are described by International Rectifier (Data Sheet IR2130, IR2235). The advantages of these solutions are the high degree of integration and the resulting low costs. Disadvantages are the limited voltage range and the limited driver performance which decreases as the dielectric strength increases.
The limited applications in connection with the required bootstrap power supply and the non-existing true galvanic separation are a great disadvantage in the prior art. For medium and high performance, it is therefore necessary to have additional optocouplers or transformers and post-amplifiers.
A monolithic potential separation is possible only by means of dielectric isolation technologies such as the subcarrier technology described by C. Y. Lu (IEEE Transactions on E. D., ED 35 (1998), pp. 230-239), wafer bonds with trench isolation according to K. G. Oppermann & M. Stoisiek (ISPSD 1996 Proc., pages 239-242) or the SIMOX technology according to Vogt et al (ISPSD 1997 Proc., pp.317-320). Because of the achievable oxide thicknesses of smaller than 2 μm, these are usually limited to isolation voltages smaller than 1200 V (usually 600 V), and they are also very expensive.
In practice, for voltages of more than 100 V, discrete optocouplers or transformers are used for potential separation between the low and high voltage sides. The advantage of transformers versus optocouplers is the bidirectional data flow for control signals. Furthermore, only with them is potential-free power transmission for the power supply of the high-voltage side possible. An advantage is that transformers require a clearly higher control capacity for signal transmission.
When discrete optocouplers or transformers are used, separate, discrete or integrated circuits are required on the low-voltage as well as on the high-voltage side. In certain cases (e.g. low performance, few analogue functions), a monolithic integration of the functions on the low-voltage side with the controller is possible.
Another conventional possibility is hybrid integration of optocoupler modules with an integrated circuit with the driver and monitoring functions (on the high-voltage side) in a special housing (Hewlett Packard Data Sheet HCPL-316., 12/97). This allows a high degree of functional integration for high voltages (of 800 V to 1200 V) as well as medium and high performance.
Only the high-voltage diode for monitoring the voltage between the collector and the emitter (VCE) because of a possible short circuit on the IGBT, the power supply for the high-voltage side and a few passive components difficult to integrate, or components for optional functions, must be supplemented discretely per branch in the driver circuit.
In the case of hybrid IGBT control circuits with galvanic separation of the primary side from the secondary side by means of optocouplers, a fast coupler is used for the signal path, and a usually slower second coupler is used for error messages.
Integrated components already exist for VCE and supply voltage monitoring on the high-voltage or secondary side (Motorola Data Sheet MC 33 153). The potential-free voltage supply for the secondary side is accomplished with a DC/DC transformer because of the greater performance required. Usually, the supply voltage is stabilized via a series-regulator circuit. If voltage is supplied on the secondary side with a DC/DC transformer, the three BOTTOM switches of an A.C. half-bridge circuit are generally combined into one voltage supply.
The functions of the low-voltage side (such as signal processing, error processing, power supply) are accomplished according to prior art by means of discrete components or, in particular the digital functions, by the controller.
In DE 198 51 186, a circuit is presented in which all functions of the primary side, such as controlling, monitoring and power supply, are accomplished by power components (MOSFET or IGBT) in a three-phase bridge circuit for a medium performance range. This integrated circuit must provide all the interface functions between the controller and the six drivers and the IGBT switches of the high-voltage side. For potential separation to the secondary side (high-voltage side), octocouplers (for control signals) according to conventional technology are used, and for the driver and monitoring functions on the secondary side, one circuit is used for each power switch.